I did a little research to see which mountains are open this long holiday weekend in late May. If you want to hike, you need to choose carefully because not all mountain resorts are open for summer yet and even if they are, many trails are still under snow.
So here are my picks for Ascension weekend that have some trails open. Not all trails are open at each location, so check the websites and webcams before heading out. For example, Männlichen in the Jungfrau region is open this weekend, but almost all the trails are closed due to snow, including the panorama trail to Kleine Scheidegg. The ropes course at Flumserberg is open but all the normal trails are closed.
Some low elevation hikes that would also be nice this weekend: